Short and long term continuous hydroxylamine feeding in a granular sludge partial nitritation reactor.

Hydroxylamine is a nitrogen intermediate of ammonium oxidizing bacteria (AOB) that can transiently accumulate during nitrification. The impact of hydroxylamine on aerobic ammonium oxidations is still obscure. In the present study the short and long term impact of hydroxylamine on partial nitritation granular sludge was investigated. Dissolved oxygen was the governing factor determining the hydroxylamine impact in short term studies with continuous hydroxylamine feeding. Continuous short term hydroxylamine feeding together with low dissolved oxygen resulted in higher hydroxylamine accumulation, higher N2O production and decreased or maintained ammonium consumption. Instead, high dissolved oxygen reduced hydroxylamine accumulation and N2O production and increased ammonium consumption. Long term continuous hydroxylamine feeding reduced ammonium consumption rate while the constant nitrite production rate indicated that dosed hydroxylamine was mainly transformed to nitrite. This indicates that hydroxylamine was preferred over ammonium as substrate. Nitrosomonas sp. was shown to be predominant during continuous hydroxylamine feeding while the side community shifted.

Remediation of bentazone contaminated water by Trametes versicolor: Characterization, identification of transformation products, and implementation in a trickle-bed reactor under non-sterile conditions.

Bentazone, an herbicide widely applied in rice and cereal crops, is widespread in the aquatic environment. This study evaluated the capacity of Trametes versicolor to remove bentazone from water. The fungus was able to completely remove bentazone after three days at Erlenmeyer-scale incubation. Both laccase and cytochrome P450 enzymatic systems were involved in bentazone degradation. A total of 19 transformation products (TPs) were identified to be formed during the process. The reactions involved in their formation included hydroxylations, oxidations, methylations, N-nitrosation, and dimerization. A laccase mediated radical mechanism was proposed for TP formation. In light of the results obtained at the Erlenmeyer scale, a trickle-bed reactor with T. versicolor immobilized on pine wood chips was set up to evaluate its stability during bentazone removal under non-sterile conditions. After 30 days of sequencing batch operation, an average bentazone removal of 48% was obtained, with a considerable contribution of adsorption onto the lignocellulosic support material. Bacterial contamination, which is the bottleneck in the implementation of fungal bioreactors, was successfully addressed by this particular system according to its maintained performance. This research is a pioneering step forward to the implementation of fungal bioremediation on a real scale.